In the manufacture of semiconductor devices, the surface of the silicon wafer must often be oxidized to form a silica layer on the surface. One conventional manner of achieving this is to place the wafer in a heated, uncontaminated container called a process tube and inject a highly pure water vapor into the process tube. The pure water vapor contacts and reacts with the surface of the wafer to produce the desired silica layer.
The pure water vapor is typically created by a hydrogen torch system housed either within or outside of the process tube. FIGS. 1 and 2 present prior art monolithic torches having a hydrogen inlet A and outlet B, and an oxygen inlet C and outlet D. This system delivers oxygen and hydrogen in separate streams into the process tube (or external combustion chamber), wherein these gases are mixed at temperatures above about 600.degree. C. The high temperature mixing produces a controlled combustion which reaches temperatures of at least about 1200.degree. C. to form water vapor.
Some conventional hydrogen torches are complicated monolithic silica tubes. However, the temperature at the exit of the hydrogen delivery tube often reaches at least about 1200.degree. C. The severity of this temperature combined with the steam atmosphere in the combustion chamber causes the typical silica delivery tube to disintegrate, initially releasing silica particles which can contaminate the semiconductor manufacturing process and eventually causing the tube to lose both dimensional and structural integrity (thereby degrading its ability to properly deliver the hydrogen).
Another family of hydrogen torches has been developed which addresses the need for performance under such extreme environmental conditions. In particular, silicon carbide torches which can tolerate the high temperature, corrosive environment of the water vapor are now available. However, relative to silica, silicon carbide is more difficult to manufacture in complex shapes and is therefore more expensive to make.
Accordingly, there is a need for a hydrogen torch which can operate in an extreme environment at reasonable cost and is easily manufactured.